Automatic telephone system



Oct 15,1946. T POWELL 2,409,586

AUTOMATIC TELEPHONE SYSTEM File d Aug. 24, 1944 3 Sheets-Shet 1 an. can

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' r WIN/RED tPowiu Patented Oct. 15, 1946 AUTOMATIC TELEPHONE SYSTEMWinfred T. Powell, Rochester, N. Y., assignor to Stromberg-CarlsonCompany, Rochester, N. Y., a corporation of New York Application August24, 1944, Serial No. 551,003

12 Claims. 1

This invention relates to automatic switching systems and moreparticularly to automatictelephone systems.

The present switching system provides a novel method of marking a givenincoming line in the bank of a finder switch by common tens and unitsrelays in cooperation with electric discharge devices, instead of theusual individual line relay marking arrangement. In addition, thissystem discloses the use of a common tens marking electric dischargedevice and a common units marking electric discharge device to provideimproved lockout operation to insure that substantially simultaneouslyoriginated calls will be completed in sequence, Also a two-relayincoming line is used which provides the usual lockout operation inconnection with revertive calls. Furthermore, this invention provides anautomatic telephone system wherein the finder switches and connectorswitches utilize only a markedly small number of controlling relays.

Other features and advantages of the invention will appear from thedetailed description and claims when taken with the drawings in which:

Figs. 1, -2 and 3, when arranged side by side in the order named,disclose an automatic telephone system of the present invention. Fig. 1illustrates in the upper left hand corner thereof, an incoming telephoneline and in the lower left hand corner thereof, a finder switch circuit.The upper right hand portion of Fig. 1 and the upper part of Fig. 2discloses a marker circuit with its common tens relays and with itscommon units marker relays, together with the controlling electronicdischarge devices. The lower right hand corner of Fig, l and the lowerleft hand part of Fig. 2 illustrate a' selector circuit while thelowerright hand corner of Fig. 2 shows a finder preselector circuit.Fig. 3 illustrates a connector switch circuit of this invention with arelated minor switch circuit to select the proper ringing frequency.

The present system illustrates a thousand line system but by theaddition of a second selector between the first selector and the"connector, here shown, the system can be increased to ten thousand linecapacity. The switches herein disclosed are of the two motion type.

The arrangement for controlling the electric discharge devices, hereinillustrated, may be generally of the type disclosed in the patent toHolden 2,252,766, granted August 19, 1941, and in the patent to Mohr2,309,525, granted January 26, 1943. j

With this brief explanation of the equipment, it

is believed that the invention will be best understood by describing theextension of a call from a calling subscriber's station A to a calledsubscribers station B. For purposes of this description, it is assumedthat thecalling line is designated #11. When the subscriber atsubstation A removes his receiver from its switchhook, a circuit iscompleted over the tip and ring conductors of the calling line, backcontacts and armatures of the cut-off relay 5, as well as the backcontacts and armatures of the lookout relay 6 through the resistor I, tothe respective sides of the battery, This circuit establishes directcurrent flow through the resistor 1 in a direction indicated by thearrow. In this way, a positive potential is applied to the #11 startelectrode in the tens marking tube 51. A negative pulser delivers anegative pulse over the #1 phase circuit I5, to the cathode |6 of thetens marking tube 9. The voltage produced across the gap in this tube,as a result of applying the negative pulse to the cathode of this tube,causes the gas in the tube to ionize and current flows from the positiveside of the direct current supply, armature and back contact of themarking release relay ll (Fig. 2), conductor l8, through the anode andcathode of tube 9, winding of the #1 tens marker relay l9 and tenslockout relay 2!], to ground. This circuit operates the relays I9 and 20and the current flow through the winding of relay 29 produces a voltagedrop across this relay which results in the immediate application of apositive potential to the cathodes of other tens marker tubes, such asfor preventing the firing of another tens marker tube inthe event ofsimultaneous calls in dinerent groups. The operation of relay l9 extendsthe start circuits of all lines in the #1 tens group to correspondingstart electrodes in all units marker tubes, such as 2|, 22 and 23. Sinceline #11 is calling, the next impulse from the #1 phase of the negativepulser fires the units marker tube 2|. The firin of the tube 2|completes a circuit from the positive pole of battery, armature.

and back contact of relay conductor 24, anode and cathode of tube 2|,winding of the units marker relay 26 and the units lockout relay 21 toground, in the same manner as resulted from the operation of the tensmarker tube 9. The voltage drop across the units lockout relay 2!results in the immediate application of a positive potential to thecathodes of the other units marker tubes for preventing the firing .of aunits marker tube in the; event of simultaneous calling.

The tens marker relay l9 marks the #1 level inthe finder banks as beingthe level in which 3 the calling line is located and the units markerrelay 26 marks the terminal in the level corresponding to the callingline. The operation of the tens lockout relay and the units lockoutrelay 2! clos a circuit for operating the start relay of the finderpreselector. This circuit extends from the grounded battery, winding,annature and back contact of the stepper magnet 28 of the preselector,winding of start relay 29, conductor 39, front contacts and armatures ofrelays 21 and 29 to ground. Start relay 29 operates in the circuit butthe stepping magnet 28 does not operate since insufficient current fiowstherethrough. It should be pointed out that the finder preselector isautomatically stepped away from a terminal associated with a busyfinder. This results from the fact that ground potential on the contacts34 of busy finders is applied through the brush 32 of the finderpreselector, armature and back contact of relay 29, back contact,armature and winding of the stepper magnet 28 to grounded battery. Thiscircuit arrangement prevents the operation of the start relay 29 at alltimes except when the brush 32 of the finder preselector is standing onan idle terminal associated with an idle finder.

Let it be assumed that the brushes of the finder preselector are restingon the terminals illustrated, which terminals are associated with thefinder illustrated in Fig. 1. Under these conditions, the operation ofthe relay 29 closes a circuit for operating the relay 34 associated withthis finder. The circuit for operating the relay 34 extends fromgrounded battery upper winding of this relay, back contact and armatureof the test relay 35, conductor 36 through the terminal of the finderpreselector associated with this finder, brush 3! of this preselector,front contact and armature of the relay 29, to ground. When the relay 34operates, the primary stepping magnet 38 of the finder is energized fromgrounded battery, winding of this magnet, its back contact and armature,front contact and armature of relay 34, back contact and armature oftest relay 35 and thence to ground over conductor 36, as previouslydescribed. Under the control of this circuit, the primary steppingmagnet, by selfinterrupting this circuit, steps the brushes 39 to 43inclusive of the finder, in a primary direction until the level brush 43of this finder encounters the level marked by the calling line.

It will be remembered that it was assumed that the calling line was #Hand, therefore, this line will appear in the first level of contacts inthe finder switch illustrated, as well as in other find- J ers in thesame group, Consequently, the finder switch will advance its brushes tothe first level of contacts and as a result of this operation, a circuitwill be closed from ground at the lower armature and front contact ofthe tens marker relay l9, conductor 44, the first level contact of thefinder, level test brush 43, armature and back contacts of relays 45 and46, conductor 41 through the make before break contacts of test relay 35to grounded battery. The test relay operates in this circuit and closesa locking circuit for itself through its front contact and armature,conductor 36 and thence to ground at the front contact and armature ofrelay 29, associated with the finder preselector. The operation of thetest relay 35 effects the release of relay 34 and also opens theself-interrupting circuit of the primary magnet 38, thereby stopping thefinder switch brushes opposite the first level of contacts in its bank.With the relay 34 released and with the test relay operated, a circuitis extended for the secondary stepping magnet 48 of the finder,traceable from grounded battery, winding of this magnet, its backcontact and armature, back contact and armature of relay 34, frontcontact and armature of relay 35, conductor 36, preselector brush 3?,front contact and armature of relay 29, to ground. Under the control ofthis self-interrupting circuit, the secondary magnet 48 steps the finderbrushes in their secondary direction, until the terminals correspondingto the calling line in the selected level are reached. Since it has beenassumed that the calling line bears the designation #11, the secondarystepping magnet 48 will advance the finder brushes one step, at whichtime a circuit will be closed from ground at the front contact andarmature of the units market relay 25, conductor 49, test brush 42,front contact and lower armature of test relay 35, lower winding ofrelay 34 to grounded battery. Relay 34 is again operated and the brushes39, 49 and 4! of the finder are now in contact with the terminals of thecalling line. This line is extended through the brushes and 4| and themake contacts of the relay 34 as well as the back contacts of relaythrough both windings of the relay 59 to ground and grounded batteryrespectively. The relay 59 operates and thereby closes an obviouscircuit for operating the slow-release relay 45. When relay 45 operatesit closes a circuit for holding the cutthrough relay 34 operated. Thiscircuit extends from grounded battery, lower winding of relay 34,conductor 52, front contact and armature of relay 34, conductor 51,front contact and armature of relay 4-5 to ground. At the lower armature54 of the relay 45, a circuit is completed for applying a dial tonethrough to the calling subscriber. The slow release relay 45 at itsarmature 55 and front contact, extends ground potential over theconductors 55 and 59, lowermost armature and front contact of relay 34,finder brush 39, sleeve conductor 53, upper winding of the cut-off relay5, to grounded battery. Cut-off relay 5 is thus operated and at itsinnermost armature and front contact extends its operating circuitthrough the lower winding of the lockout relay 5 to grounded battery.Thus, both relays 5 and 5 are operated. The mentioned ground at thearmature 55 and front contact of the slow releasing relay 45, isextended over conductors 56 and 59, finder preselector brush 32 throughthe armature and front contact of the relay 29, winding of the markerrelease relay ll, to grounded battery. When the relay ll operates, itinterrupts at its upper armature and back contact, the operatingcircuits of all the marker tubes and marker relays associated therewithwhich were operated in response to the call on the calling line #11.

The release of the tens lockout relay 25 and the units lockout relay2'5, opens the circuit that has been holding the relay 29 of thepreselector operated. This relay releases and extends the conductor 59characterized by ground potential at the armature and front contact ofthe relay 45, thence through the back contact, armature and winding ofthe stepping magnet 28, to grounded battery. Under the control of thiscircuit, the finder preselector stepping magnet 28 advances thispreselector away from the trunk circuit which it has just assigned, tothe next idle trunk to be used. The release of the start relay 29 alsoopens the circuit and effects the release of the marker release relay Hwhich re- '5 stores positive potential on the marker tube circuits. Therelease of the relay 29 also effects the release of the test relay 35 ofthe f nder.

Since the calling party hears the dial tone, he operates the dial at hissubstation to generate the several series of impulses corresponding tothe designation of the called subscribers line. Let it be assumed that#2 corresponds to the hundreds digit of the desired number. In responseto the mentioned two impulses corresponding to the hundreds digit, therelay 50 will be intermittently released twice and will then remainenergized. On the first release of the relay 59, an operating circuit iscompleted for the primary motor magnet v6| of the selector, whichcircuit extends from grounded battery, winding of this magnet andwinding of the slow releasing relay 62 in series, front contact andarmature of relay 45, back contact and armature of relay st, to groundat the armature and back contact of relay 45. As soon as the selectorswitch takes its first step in the primary direction, it closes itsprimary off-normal contacts 63 and opens it primary off-normal contacts19. A circuit is now completed for operating the stepping relay 6 1 fromgrounded battery, winding of this relay, off-normal contacts 63,armature and front contact of relay 62, front contact and armature 55 ofrelay 45, to ground. Stepping relay M, on operation, closes a lockingcircuit for itself from grounded battery through its winding, oif-normalcontact 63, back contact and armature of the secondary motor magnet 65,conductor 55, back contact and armature of the cut-through relay 46,front contact and armature of relay 64 to ground. At the end of thefirst impulse, the relay 5B energizes, as a result of which, thechangeover relay 65 and the primary magnet 5| have their operatingcircuits interrupted, causing the primary magnet to release but thechange-over relay 62 remains operated due to its slow releaslllgcharacteristic. The action of the primary motor magnet, of course, stepsthe selectorswitch in itsprimary direction. In response to the secondand last impulse of the hundred series, the impulse relay 5t againreleases so that the primary magnet iii operates again for advancing thebrushes of the selector switch to the second level of this switch. Atthe close of the second impulse, the relay 59 remains energized for aperiod long enough to permit the release of the changeover relay B2. Inresponse to therelease of relay 62, a circuit is closed for thesecondary motor magnet (55 from grounded battery, winding of thismagnet, front contact and armature of the stepping relay 64, backcontact and continuity spring of relay 62, front contact and armature 55of relay 45, to ground. As soon as the secondary magnet 65 operates, itinterrupts at its armature Bl and back contact, the locking circuit ofsteppin relay 64, previously described. Relay 64 releases, whereupon atits lower armature and front contact it interrupts the operating circuitof the secondary magnet 65. The release of magnet 65 again closes acircuit for the stepping relay 64. This circuit now extends fromgrounded battery, winding of relay til, off-normal contact E3, backcontact and armature 6'! of the secondary magnet, back contact andarmature of relay 46, conductor 68, test brush H, to ground on the testterminal 14, if the first trunk in the second level of the selectorhappens to be busy. With the stepping relay E l'again operated, thesecondary magnet 65 again operates to advance the brushes of theselector to the second set of terminals corresponding to the secondtrunk in the selected group. As long as the selector test brush 'Hencounters busy terminals, such as M, of trunks in use, the groundpotential on these terminals will prevent the operation of thecutthrough relay 46 since this cut-through relay will be short-circuitedunder that condition. When the selector test brush H encounters the testterminal 14 of an idle trunk, a condition indicated by the absence ofground potential on its test terminal, then the cut-through relay 46 isoperated.

When the cut-through relay 46 operates, it disconnects the calling linefrom the relay 50 of the selector and extends this calling line throughthe selector brushes :2 and 13, back contacts and continuity springs ofrelay I5, windings of the impulse relay it, .to ground and groundedbattery respectively. This circuit operates the relay 1B which in turncauses the slow-releasing relay H'- to operate. The release of the relay5B of the selector as well as the operation of the cut-through relay 46associated therewith, releases slow-releasing relaytS of the selector.However, before this relay releases, ground potential applied at theconnector that has been seized is applied over the conductor 18 forlocking the cut-through relay 48 operated. This ground potential is alsoapplied over the conductors 5t and 59, brush 39 of the finder, windingsof the cut-off relay 5 and lockout relay 6 for holding them operated.This ground potential is also extended over conductor 59 to the finderpreselector for keeping busy at this point the trunk that is in use.Since the dial tone is applied through the primary off-nor.- malcontacts 19, this tone will be disconnected from the calling line assoon as this selector has taken its first step.

After the connector is seized in the manner already described, a seriesof impulses corresponding respectively to the tens, units and stationdigits are dialed by the calling subscriber. In response to the firsttens digit, the impulse relay it of the connector releases. This closesa circuit for operating the change-over relay 8B and the primarystepping magnet 81 in series. This circuit extends from groundedbattery, winding of magnet 8|, back contacts and armatures of relays 82and 83, winding of the change-over relay 80, armature andback contact ofthe busy relay 84, front contact and armature of relay TI, back contactand armature of the impulse relay lt, to ground. The change-over relay80 remains operated during the tens series of impulses but the primarymagnet 8| responds to each impulse to advance the connector switchbrushes 86, 81 and 88 in their primary direction.

At the close of the tens series of impulses, the change-over relay 80releases and thereby closes a circuit for operating the transfer relay83. This circuit extends from grounded battery, winding of relay 83,back contact and armature of the cut-in relay 89, back contact andarmature of the ringing relay 82, front contact of impulse relay 16,primary oif-normal contacts 90, now closed, back contact and armature ofthe change-v over relay an, to ground. Transfer relay 83 on operatingcloses a locking circuit for itself through its lower front contact andarmature, lowermost back contact and armature of the ringing relay 82,conductors 18 and 93, front contact and armature of relay 11, to ground.

The connector is now in condition to receive the units series ofimpulses, and when the ,calling subscriber dials the units series ofimpulses,

the impulse relay 16 will be intermittently energized and deenergized,as described in connection with the tens series of impulses. In thisinstance, however, the change-over relay 3E! and the secondary motormagnet 91 now operate in series, inasmuch as transfer relay 83 hatransferred the control of the impulse relay from the primary motormagnet 8| to the secondary motor magnet 9|.

In response to the first impulse of the units digit, the change-overrelay 80 operates as before. This in turn operates the ringing relay 82from grounded battery, resistance, winding of this relay, front contactand armature of the transfer relay 83, front contact and armature ofchangeover relay 89. The ringing relay on operating closes a lockingcircuit for itself through its lowermost front contact and armature, toground over conductor '8. The operation of the relay 82 interrupts theprevious circuit for the transfer relay 83, but this relay is now lockedoperated through its lower front contact and armature, armature andfront contact of the change-over relay to ground over conductor l8.

At the close of the units series of impulses, the change-over relay 80releases and this in turn opens the locking circuit of the transferrelay 83 which also releases.

At the close of the units series of impulses, the connector brushes 86,81 and 88 are in contact with the terminals of the called line. It is,therefore, in order to test this called line to determine its busy oridle condition. If the called line is busy, ground potential is extendedthrough the connector test brush 88, armature and front contact of theringing relay 82, armature and front contact of the transfer relay 83,back contact and armature of the change-over relay 89, back contact,continuity spring and winding of the busy relay 84, to grounded battery.Busy relay 84 locks itself operated. When the busy relay is operated, inthe case of a call to a busy line as just indicated, the characteristicground potential applied to the test brush 88 is opened and the cut-inrelay 89 is not operated because the operating circuit of this relay isopened at a back contact of the busy relay 84. When the busy relay isoperated in the manner described, the busy tone is applied overconductor 92 to the calling line. The busy relay 84 at its uppermostarmature and back contact interrupts the circuits to the primary andsecondary motor magnets so that future impulses will not operate theconnector switch.

If the called line is not busy, no ground potential will be applied toits test terminal and no ground potential is applied to the test brush8B for operating the busy relay 84. Thus, when the transfer relay 8-3eventually releases, ground is extended through the back contacts andarmatures of relays 84 and 83, front contact of the ringing relay 32 tothe test brush 88 for the purpose of making the called line busy and foroperating the cut-off relay of that line.

It is now in order to dial the series of impulses corresponding to thedesignation of the desired station on the called line. Impulsescorresponding to this digit operate the impulse relay 76 as before.However, in response to these impulses, the motor magnet 94 of the minoror frequency selecting switch, is operated. The circuit for effectingthis operation extends from grounded battery, winding of the magnet 94,front contact and armature of ringing relay 82, back contact andarmature of transfer relay 83, change-over relay 80, armature and backcontact of busy relay 84, front contact and armature of relay TI, toground, at the back contact and armature of the relay 16. Thechange-over relay operates in series with magnet 94 and relay 8:] at itsupper front contact and armature closes a circuit around the backcontact and armature of the busy relay 84. This is necessary becauserelay 84 is going to be operated as the station digit is dialed. In thisdistance, the circuit for operating the busy relay 84 extends fromground at the off-normal contacts 96 of the minor switch, conductor 91,front contact and armature of change-over relay 80, back contact,continuity spring and winding of busy relay 84, to grounded battery. Thecut-in relay 89 is operated before the busy relay 84 is operated duringthe station selection on a call to an idle lin thereby distinguishingbetween the idle and the busy condition, since the relay 84 is operatedin both cases. At the conclusion of the units impulses, the change-overrelay 80 releases and thus completes a circuit for operating the cut-inrelay 89. This circuit is traceable from grounded battery, winding ofthis relay, back contact and armature of relay 84, front contact andarmature of relay 82, front contact of impulse relay I6, off-normalcontacts 90, back contact and armatur of the change-over relay 80, toground. The cut-in relay 89, on operating, closes a locking circuit foritself over the conductor 79. With the cut-in relay 89 and the busyrelay 84 operated, reverting ringing tone is connected to the callingline while ringing current of the proper frequency is extended throughthe brush of the minor or frequency selecting switch, conductor 98,winding of the trip relay 99 and thence through the tip and ring brushesof the connector and over the tip and the ring sides of th called lineand through the ringer of the wanted station on this line. When thecalled party answers, the trip relay 99 energizes and at its armatureand front contact short-circuits the ringing relay 82, which releases.With the cutin relay 89 operated as previously described and with theringing relay 82 released, the connection is completed between thecalling and the called stations.

Talking battery is supplied to the called line through the windings ofthe relay 15. This relay is maintained energized by this talking currentand it reverses the battery supply to the calling line through thewindings of the relay 16 for purposes of supervision or metering.

When the calling party replaces his receiver on its switch hook toterminate the connection, the relay l6 and the slow releasing relay 1'!of the connector are released in turn for operating the release magnetHill of the connector through an obvious circuit. The relay 71 at itsupper back contact and armature, also closes a circuit for the releasemagnet l9! of the minor or frequency selecting switch. The operation ofthese release magnets restores the connector and frequency selectingswitches to their normal positions. The release of relay 11 alsodisconnects ground potential from the conductor 93. This is eifective torelease the cut-in relay 89, and busy relay 84 of the connector. Inaddition, the release of relay 1! is effective to release the cutthroughrelay 46 of the selector. The release of the cut-in relay 89 as well asthe release of the connector switch, disconnects ground from the testbrush 88 of the connector for clearing the called line circuit. Therelease of the cut-through relay 4B of the selector closes an obviouscircuit for operating the release magnet I02 of the selector to eiiectrelease of this switch. The removal of ground potential from the brush88 effects the release of the cut-off relay and the lockout relay of thecalled line, which relays correspond to the relays 5 and 6 of thecalling line. The release of the cut-through relay 45 ofthe selectorremoves ground from the lower winding of the cut-through relay 34 of thefinder. This releases the relay 34 and closes a circuit for operatingthe release magnet l (M of the finder for restoring this switch to itsnormal position.

In the event that the calling subscriber at substation A desires tocommunicate with. a substation on his own line, commonly referred to asa revertive call, the subscriber at A dials the number of the wantedsubstation which in the case of a revertive call is prefixed by aspecial digit. The special digit selects a revertive call circuit of thetype disclosed in the patent to Powell 2,325,877, granted August 3,1943. Under the control of the revertive call circuit, called multiplecontacts of the calling line A will be seized. In the course ofextending the calling line to the revertive call circuit, ground isapplied to the sleeve conductor 58 of this line by way of a finderbrush, such as 39 (Fig. 1). With ground on sleeve conductor 58, thecut-off relay 5, is energized through its upper winding to groundedbattery. The slowrelea'sing lockout relay 6 is thereupon operated fromgrounded battery, lower winding of this relay, front contact and innerarmature of relay 5, to the grounded sleeve conductor 58. In accordancewith the usual practice, the calling party replaces his receiver on itsswitch hook whereupon the calling and called stations have ringingcurrent alternately applied thereto. When the subscriber at one of thesestations answers, the ringing current is tripped and the selector andfinder are released in the manner indicated in the mentioned patent.This removes ground from conductor 58 causing relay 5 to release.However, lockout relay 5 is slow releasing and, therefore, does notrelease, but is held operated from grounded battery, lower winding ofthis relay, its inner front contact and armature, back contact andarmature of cut-off relay 5, thence over the two sides of the line inseries, armature and back contact of relay 5, middle armature and frontcontact of the relay 6, and through the upper, winding of this relay toground. The talking battery is supplied to both subscribers over thecircuit last described. When both parties to the revertive call replacetheir receivers on their respective switch hooks, the lockout relay 5releases to restore the line circuit to its original condition.

What I claim is:

1. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines being arranged in primary sets according toone grouping, said incoming lines being arranged in secondary setsaccording to another grouping with only one incoming line common to agiven primary set and to a given secondary set, a primary relayindividual to each primary set of lines and a secondary relay individualto each secondary set of lines, and electrical discharge means actuatedunder the control of any given one of said incoming lines for operatingthe primary relay and the secondary relay individual to the two sets oflines including said given incoming line, said last-mentioned primaryrelay and secondary relay governing the operation of said switchingmeans to interconnect saidgiven incoming line to an outgoing line.

2. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines terminating in contacts arranged in primarygroups along one direction and arranged in secondary groups alonganother di-- rection, each incoming line being common to only oneprimary group and one secondary group, a primary relay common to eachprimary group and a secondary relay common to each secondary group,means including an electric discharge path individual to and controlledover a given incoming line for actuating the primary relay commonthereto, means including another electric discharge path individual toand also controlled over said given incoming line for actuating thesecondary relay common to the given line, and switching means governedby the actuated primary and secondary relays operating to engage thecontacts of said given incoming line.

3. In a telephone system, a plurality of incoming lines arranged inprimary sets according to one grouping, said lines being arranged insecondary sets according to another grouping with only one incoming linecommon to a given primary set and to a given secondary set, a primaryrelay and a primary electric discharge device individual to each primaryset of lines, a secondary relay and a secondary electric dischargedevice individualto each secondary set of lines, each discharge devicecomprising a cathode and an anode common to its set of lines and acontrol electrode individual to each incoming line, means including anygiven one of said incoming lines and a control electrode in the primarydischarge device as well as a control electrode in the secondarydischarge device and said given incoming line for operating the primaryrelay and the secondary relay individual to the two sets of incominglines including said given incoming line, said last-mentionedl primaryrelay and secondary relay governing the operation of said switchingmeans to interconnect 'said given incoming line to an outgoing line.

4. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines terminating in contacts arranged in primarygroups along one direction and arranged in secondary groups alonganother direction, each incoming line being common to only one primarygroup and one secondary group, a primary electric discharge path and asecondary electric discharge path individual to each incoming line, theprimary electric paths and the secondary electric paths having the samegrouping as said incoming lines, a primary relay common to each primarygroup and a secondary relay common to each secondary group, meansincluding an electric discharge path individual to and controlled over agiven incoming line for actuating the primary relay common thereto,means including another electric discharge path individual to and alsocontrolled over said given incoming line for actuating the secondaryrelay common to the given line, and switching means governed by theactuated primary and secondary relays operating to engage the contactsof said given incoming line.

5. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines terminating in contacts arranged in primarygroups along one direction and arranged in secondary groups alonganother direction, each incoming line being common to only one primarygroup and one secondary group, a primary electric discharge path and asecondary electric discharge path individual to each incoming line, theprimary electric paths and the secondary electric paths having the samegrouping as said incoming lines, a primary relay common to each primarygroup and a secondary relay common to each secondary group, meansincluding an electric discharge path individual to and controlled over agiven incoming line for actuating the primary relay common thereto,means including another electric discharge path individual to and alsocontrolled over said given incoming line for actuating the secondaryrelay common to the given line, means insuring the completion of onlyone primary electric discharge path and onl one secondary electricdischarge path at a time in the respective groups, and switching meansgoverned by the actuated primary and secondary relays operating toengage the contacts of said given incoming line.

6. In a telephone system, plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines terminating in contacts arranged in primarygroups along one direction and arranged in secondary groups alonganother direction, each incoming line being common to only one primarygroup and one secondary group, a primary electric discharge path and asecondary electric discharge path individual to each incoming line, theprimary electric paths and the sec ondary electric paths having the samegrouping as said incoming lines, a primary relay common to each primarygroup and a secondary relay common to each secondary group, meansincluding an electric discharge path individual to and controlled over agiven incoming line for actuating the primary relay common thereto,means including another electric discharge path individual to and alsocontrolled over said given incoming line for actuating the secondaryrelay common to the given line, means rendering the electric dischargepaths of each group effective in sequence, and switching means governedby the actuated primary and secondary relays operating to engage thecontacts of said given incoming line.

'7. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, said incoming lines terminating in contacts coordinatelyarranged in primary rows extending in one direction and also arranged insecondary rows extending at right angles to said first rows, a primaryelectric discharge path for each incoming line in each primary row, asecondary discharge path for each incoming line in each secondary row,means responsive to the initiation of a call over a given incoming linefor completing the primary discharge path and the secondary dischargepath individual to the given incoming line, and switching means governedby the completed primary discharge path and by the completed secondarydischarge path for interconnecting the contacts of the given incomingline with one of said outgoing lines.

8. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines being arranged in primary groups and insecondary groups, each incoming line being common to only one primarygroup and one secondary group, a primary electric discharge path and asecondary electric discharge path individual to each incoming line, theprimary discharge paths and the secondary discharge paths having thesame grouping as said incoming lines, means including an electricdischarge path individual to and controlled over a given incoming linefor marking the primary group of said given incoming line, meansincluding the secondary electric discharge path individual to and alsocontrolled over said given incoming line for marking the same in saidsecondary group, said switching means being governed by said markingsfor interconnecting said given incoming line with an outgoing line.

9. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, said incoming lines terminating in contacts coordinatelyarranged in primary rows extending in one direction and also arranged insecondary rows extending at right angles to said first rows, a primaryelectric discharged path for each incoming line in each primary row, asecondary discharge path for each incoming line in each secondary row,means responsive to the initiation of a call over a given incoming linefor completing the primary discharge path and the secondary dischargepath individual to the given incoming line, switching means governed bythe completed primary discharge path and by the completed secondarydischarge path for interconnecting the contacts of the given incomingline with one of said outgoing lines, and means for temporarilydisabling the other primary discharge paths and the other secondarydischarge paths related to primary and secondary rows including thegiven incoming line, while the discharge paths of this line are completed.

10. In a telephone system, a plurality of incoming lines, a plurality ofoutgoing lines, automatic switching means for interconnecting saidlines, said incoming lines being arranged in primary groups and insecondary groups, each incoming line being common to only one primarygroup and one secondary group, a primary electric discharge path and asecondary electric discharge path individual to each incoming line, theprimary discharge paths and the secondary discharge paths having thesame grouping as said incoming lines, means including an electricdischarge path individual to and controlled over a given incoming linefor marking the primary group of said given incoming line, meansincluding the secondary electric discharge path individual to and alsocontrolled over said given incoming line for marking the same in saidsecondary group, and means for rendering said groups of primary andsecondary electric discharge paths effective in sequence, said switchingmeans being governed by said markings for interconnecting said givenincoming line with an outgoing line.

11. In a telephone system, a plurality of incoming lines arranged inprimary groups according to one grouping, said incoming lines beingarranged in secondary groups according to another grouping with only oneline common to a given primary group and to a given secondary group, aprimary electric discharge device individual to each primary group oflines, a second ary electric discharge device individual to eachsecondary group of lines, each discharge device comprising a cathode andan anode-common to its group of lines and a control electrode individualto each incoming line in its group, means coming line for causingcurrent to flow through the resistor individual thereto whereby adifference in potential is established across said resistor for markingthe primary group of the given incoming line as Well as for marking saidgiven incoming line in the group, and switching means responsive to saidmarkings for seizing said incoming line.

12. In a telephone system, a plurality of incoming lines arranged inprimary groups according to one grouping, said incoming lines beingarranged in secondary groups according to another grouping with only oneline common to a given primary group and to a given secondary group, aprimary electric discharge device individual to each primary group oflines, a secondary electric disi4 charge device individual to eachsecondary group of lines, each discharge device comprising a cathode andan anode common to its group of lines and a control electrode individualto each incoming line in its group, means responsive to the initiationof a call on said incoming line for causing current to flow through theresistor individual thereto whereby a difference in potential isestablished across said resistor for marking the 10 primary group of thegiven incoming line as Well 15 discharges effective in sequence.

WINFRED 'r. POWELL.

